确定EF实体中ConstraintException的来源

Question

我有一个实体类，其中有一堆非空字符串属性。如果我尝试设置这些为空一个，我得到一个ConstraintException和消息“这个属性不能被设置为空值。”

没有跟踪变量设置为分配前的各属性的名称，有没有一种方法可以确定哪个属性分配导致异常被抛出？

Answer 1

在您的POCO类中，您可以使用Checker模式进行此验证。使用构造函数注入不可空属性注入。

public class Product:Entity<long> 
{ 
    public Product(string description, string productNo, double? unitPrice, Category category) 
    {   

     Check.Require(unitPrice.HasValue, "Unit price can not be null in Product"); 
     Check.Require(!string.IsNullOrEmpty(description), 
       "Description can not be null in Product");    

     Check.Require(!string.IsNullOrEmpty(productNo), 
      "Product number can not be null in Product"); 

     Check.Require(category != null, "Category can not be null in Product"); 

     UnitPrice = unitPrice.Value; 
     Description = description; 
     ProductNumber = productNo; 
     Category = category; 
    } 



    /// <summary> 
    /// Gets or sets the product id. 
    /// </summary> 
    /// <value> 
    /// The product id. 
    /// </value> 
    public int ProductId { get; set; } 

    /// <summary> 
    /// Gets or sets the name. 
    /// </summary> 
    /// <value> 
    /// The name. 
    /// </value> 
    public string Name { get; set; } 

    /// <summary> 
    /// Gets or sets the category id. 
    /// </summary> 
    /// <value> 
    /// The category id. 
    /// </value> 
    public long CategoryId { get; set; } 

    /// <summary> 
    /// Gets or sets the category. 
    /// </summary> 
    /// <value> 
    /// The category. 
    /// </value> 
    public Category Category { get; set; } 

    /// <summary> 
    /// Gets or sets the unit price. 
    /// </summary> 
    /// <value> 
    /// The unit price. 
    /// </value> 
    public double UnitPrice 
    { 
     get; 
     set; 
    } 

    /// <summary> 
    /// Gets or sets the description. 
    /// </summary> 
    /// <value> 
    /// The description. 
    /// </value> 
    public String Description 
    { 
     get; 
     set; 
    } 

    /// <summary> 
    /// Gets or sets the product number. 
    /// </summary> 
    /// <value> 
    /// The product number. 
    /// </value> 
    public string ProductNumber 
    { 
     get; 
     set; 
    } 
} 

}

public class Check 
{ 
     /// <summary> 
    /// Requires the specified assertion. 
    /// </summary> 
    /// <param name="assertion">if set to <c>true</c> [assertion].</param> 
    /// <param name="message">The message.</param> 
    public static void Require(bool assertion, string message) 
    { 
     if(!assertion) 
     { 
      throw new PreConditionException(message); 
     } 
    } 

    /// <summary> 
    /// Ensures the specified assertion. 
    /// </summary> 
    /// <param name="assertion">if set to <c>true</c> [assertion].</param> 
    /// <param name="message">The message.</param> 
    public static void Ensure(bool assertion, string message) 
    { 
     if (!assertion) 
     { 
      throw new PostConditionException(message); 
     } 
    } 
} 

/// <summary> 
/// Exception raised when a precondition fails. 
/// </summary> 
public class PreConditionException : Exception 
{ 
    /// <summary> 
    /// Initializes a new instance of the <see cref="PreConditionException"/> class. 
    /// </summary> 
    /// <param name="message">The message.</param> 
    public PreConditionException(string message):base(message) 
    { 

    } 
} 

/// <summary> 
/// Exception raised when a postcondition fails. 
/// </summary> 
public class PostConditionException:Exception 
{ 
    /// <summary> 
    /// Initializes a new instance of the <see cref="PostConditionException"/> class. 
    /// </summary> 
    /// <param name="message">The message.</param> 
    public PostConditionException(string message):base(message) 
    { 

    } 
} 

Answer 2

您可以访问堆栈跟踪？它会像'MyEntity.set_MyNotNullableProperty42'这样的东西告诉你哪个属性被设置为null。